라즈베리 파이 PWR ACT - lajeubeli pai PWR ACT

If your Raspberry Pi board isn't booting, and the green 'Act' LED is flashing, count the number of flashes to look up which of the following issues that indicates. This is an excerpt from the full forum posts at https://www.raspberrypi.org/forums/viewtopic.php?t=58151;

Error ACT LED patterns (RPI up to but NOT including Pi4)
revision March 9, 2020

While booting, the ACT LED should blink in an irregular pattern, indicating that it is reading from the card. If it starts blinking in a regular, Morse code-like pattern, then it is signalling an error.

If it blinks just once, it could be that you have a Raspberry Pi with SDRAM from Micron. If the processor has a logo showing an M with an orbit around it, then using the latest software should solve your problem. Also make sure you are using a 4GB SD card, as a 2GB won't work in this particular case.

These are the other patterns that the ACT LED might show during a failed boot, together with their meanings (the below blink codes are NOT valid for a RPI4, read the RPI4 section for ACT LED flash messages!):

• 3 flashes: start.elf not found
• 4 flashes: start.elf not launch-able (corrupt) See below:
• 7 flashes: kernel.img not found
• 8 flashes: SDRAM not recognized. You need a newer bootcode.bin/start.elf firmware, or your SDRAM is damaged

If you have an older model of the Pi, you should note that firmware before 20th October 2012 required loader.bin, and the meaning of the flashes was slightly different:

• 3 flashes: loader.bin not found
• 4 flashes: loader.bin not launch-able (corrupt) See below:
• 5 flashes: start.elf not found
• 6 flashes: start.elf not launch-able
• 7 flashes: kernel.img not found

Potential reason for 4 flashes
Note that 4 flashes could be an indication of a more or less broken SD-card connector. If Databit 1 is connected, but one of the other three Databits doesn't make contact, so the SD-card only works in 1-bit (SPI) mode, then this will lead to the four flashes error! Check if all pins of your card holder make good contact with the card!

Try the most basic set-up
If you are having a hard time getting the Pi to boot, try stripping it down to its most basic set-up. Disconnect any extraneous USB devices, and try booting with only the video and the power cable connected. If you have to press keys to switch video mode, you will need to connect some kind of keyboard, but try it with the most basic, no-frills USB-keyboard. This can help ease the boot process in some circumstances.

Error ACT LED patterns (Pi4 ONLY)
revision 2020-06-05
bootloader 2020-09-14

Unlike previous Raspberry PI's the RPI4B boots with the use of code from a built-in EEPROM, which means it can use more complex boot code with more flexibility, and the ability to add new features (like Network and USB booting). Consequently, when the new boot code doesn't detect a valid start.elf file on the SD-card, it will blink the activity LED four times with an interval between the four blinks.

So, unlike other RPI's blinking the ACT LED (in a regular pattern), on the Pi4, it doesn't mean the SD-card is detected and is booting, it means the EEPROM code cannot find the SD-card (start.elf). Connect a monitor on HDMI0 (nearest the power port) for the boot failure reason.

LED warning flash codes
If a Pi fails to boot for some reason or has to shut down, in many cases an LED will be flashed a specific number of times to indicate what happened. The LED will blink for a number of long flashes (0 or more), then short flashes, to indicate the exact status. In most cases, the pattern will repeat after a 2-second gap.

so:

• if the ACT LED blinks in a regular four blink pattern, it cannot find bootcode (start.elf).
• if the ACT LED blinks in an irregular pattern, then booting has started.
• If the ACT LED doesn't blink, then the EEPROM code might be corrupted. Try again without anything connected to make sure.